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Ewerdwalbesloh, Julia A.; Palva, Satu; Rösler, Frank; Khader, Patrick H. (13. July 2016): Neural correlates of maintaining generated images in visual working memory. In: Human Brain Mapping, Vol. 37, No. 12: pp. 4349-4362
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How are images that have been assembled fr om their con stituting elements maintained as a coherent representation in visual working memory (vWM)? Here, we compared two conditions of vWM maintenance that only diff ered in how vWM contents had been created. Participants maintained images that they either had to assemble from single features or that they had perceived as complete objects. Object complexity varied between two and four features. We analyzed electroencephalog ram phase coupling as a measure of cortical connectivity in a time interval immediately before a prob e stimulus appeared. We assumed that during this time both groups maintained essentially the same images, but that images constructed from their elements wou ld require more neural coupling than images based on a complete percept. Increased coupling between frontal and parietal-to-occipital cortical sources was found for the maintenance of constructed in comparison to nonconstructed objects in the theta, alpha, beta, and gamma frequency bands. A similar pattern was found for an increase in vWM load (2 vs. 4 features) for nonconstructed objects. Under increased construction load (2 vs. 4 features for constructed images ), the pat tern was re stric ted to fronto-parietal couplings, suggesting that the fronto-parietal attention network is coping with the higher attentional demands involved in maintaining constructed images, but without increasing the communication with the occipital visual buffer in which the visual representations are assumed to be stored. We conclude from these findings that the maintenance of constructed images in vWM requires additional attentional processes to keep object elements together as a coherent representation.